If your not going to MNSSHP do HalloWishes. If you are going to the party go on a Wishes night. We will be going to MNSSHP and going to CG on a Wishes night (with plans to also see MSEP and Wishes on yet another night). At least, that is what our plan is right now.
On the nights when the Magic Kingdom has Mickey's Not So Scary Halloween Party then the California Grill will play the music for it, so it's not just the regular Wishes music that's always played up there.
Thanks for the input. We're doing Cali Grill on our adult-only trip. We've done MNSSHP before (which I thoroughly enjoyed), but won't be on this trip. I'm leaning toward doing the Hallowishes - hadn't thought about the music being piped int, probably my final decision point. The MNSSHP night fits better into our schedule also.